Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. A magnetic hard disk drive is an example of an information storage device that includes one or more heads that can both read and write, but other information storage devices also include heads—sometimes including heads that cannot write. For example, in an optical disk drive, the head will typically include a mirror and objective lens for reflecting and focusing a laser beam on to a surface of the disk. In magnetic recording applications, the head will typically include a transducer having an inductive writer and a magnetoresistive reader.
In a modern magnetic hard disk drive device, each head is a sub-component of a head gimbal assembly (HGA) that typically includes a suspension assembly with a laminated flexure to carry the electrical signals to and from the head. The HGA, in turn, is a sub-component of a head stack assembly (HSA) that typically includes a plurality of HGAs, an actuator, and a flexible printed circuit (FPC) that includes a flex cable. The plurality of HGAs are attached to various arms of the actuator, and each of the laminated flexures of the HGAs has a flexure tail that is electrically connected to the FPC of the HSA.
Modern laminated flexures typically include conductive copper traces that are isolated from a stainless steel structural layer by a polyimide dielectric layer. So that the signals from/to the head can reach the FPC at the actuator body, each HGA flexure includes a flexure tail that extends away from the head along the actuator arm and ultimately attaches to the FPC adjacent the actuator body. That is, the flexure includes traces that extend from adjacent the head and terminate at electrical connection points at a terminal region of the FPC.
The FPC includes electrical terminals that correspond to the electrical connection points of the flexure tails. The FPC also includes a flex cable that includes a number of electrical traces to be connected to the electrical traces of the flexure tails. The FPC electrical traces carry signals along the flex cable from/to a printed circuit board assembly (PCBA) to/from the heads, as the heads write and read information recorded in concentric circular tracks on the disks.
The flex cable is typically longer than the shortest length required to span the distance between the actuator assembly and the flex bracket, because it is not desired for the flex cable to constrain the angular range of motion of the actuator. The excess length in the flex cable forms a curve that allows the actuator assembly to be electrically coupled yet mechanically compliant to the applied torque (e.g. from a voice coil motor). Still, the flex cable exerts some biasing torque on the actuator, which must be overcome and compensated for by the voice coil motor.
The FPC may be designed to include a flex stiffener at the FPC termination region adjacent the actuator body, to support and facilitate attachment of the FPC terminal region to the actuator body, and to help set and control a desired exit angle θ of the flex cable from the actuator body. Typically, the flex stiffener causes a bend, between the flex cable and the FPC terminal region, that is about a bend axis that is parallel to the pivot axis of the actuator.
However, such flex stiffener designs may present challenges to realizing certain contemporary trends in disk drive technology: reducing the size of disk drives, and/or increasing the number of conductors per head. Specifically, the maximum height specified for modern disk drives may be considerably less than that specified for disk drive designs of the past. Such trend may conflict with another trend to embed more functionality within each read/write head, since doing so often requires more numerous electrical conductors to be connected to each read/write head. Having more numerous electrical conductors would tend to increase the height of the flex cable, and the FPC terminal region. Hence, there is a need in the art for a FPC design that can accommodate additional electrical conductors in the flex cable without excessive height in the FPC terminal region.